The Rotor Position Estimation Error Improved Method for Sensorless Starting Control of Brushless Synchronous Machine

This article proposed a sensorless starting control method for the brushless synchronous machine with the indirectly injected high-frequency signal, where the high-frequency signals are injected into the stator windings of the main exciter instead of the main generator. The impact of the nonlinear links of the rotary rectifier and various filters on the rotor position estimation error during the asynchronous demodulation method is analyzed in detail. Since the phase delay of the bandpass filter and the low-pass filter will deteriorate the zero-crossing points of the envelope curve, the signal restoration module could not restore the sinusoidal envelope curve accurately, then, the estimated rotor position error is expanded with the increasing of rotor speed in the starting process. Therefore, a novel mathematical analysis method with fewer filters for the rotor position demodulation is presented to improve the estimated rotor position error compared to the traditional method, and the feasibility and effectiveness of the proposed method are verified by the comparison of the simulation and experimental results.